How can I access my object's volume to compare then and display the most common size (small, medium, large, etc.) in c++?

so within my project I have to display the popular shapes, color percentages and most common size based on volume, I was able to print the popular shape and color using my global arrays:

int numColor[CC_COUNT];
double rawColor[CC_COUNT] = { 100.0, 100.0, 100.0, 100.0 };
int numShapes[SC_COUNT];

ObjectData ReadObjectData()
{
    ObjectData object;
    object.index = g_objectCount;
    object.valid = true;
    object.printed = false;

    printf("Please enter the shape and color of object: ");
    scanf("%d%d", &object.shape, &object.color);

    const double PI = 3.14;
    int i = 0;

    switch(object.shape){
        case SC_CUBE:
            printf("Please enter cube's side length: ");
            scanf("%lf", &object.dimen[i]);
            object.volume = pow(object.dimen[i],3);
            printf("The volume is %.4lf\n", object.volume);
            break;

        case SC_CUBIOD:
            object.volume = 1;
            printf("Please enter the cubiod's side lengths\n");
            for(i = 0; i < 3; i++){
                printf("Side %d: ", i+1);
                scanf("%lf", &object.dimen[i]);
                object.volume = object.volume * object.dimen[i];

            }
             printf("The volume is %.4lf\n", object.volume);
            break;

        case SC_SPHERE:
            printf("Please enter the sphere's radius: ");
            scanf("%lf", &object.dimen[i]);
            object.volume = (4.0 / 3) * PI * pow(object.dimen[i], 3);
             printf("The volume is %.4lf\n", object.volume);
            break;

        case SC_CYLINDER:
            printf("Please enter the cylinder's radius and height: ");
            scanf("%lf%lf", &object.dimen[0], &object.dimen[1]);
            object.volume = PI * pow(object.dimen[0], 2) * object.dimen[1];
             printf("The volume is %.4lf\n", object.volume);
            break;

        case SC_CONE:
            printf("Please enter the cone's radius and height: ");
            scanf("%lf%lf", &object.dimen[0], &object.dimen[1]);
            object.volume = (1 / 3.0) * PI * pow(object.dimen[0], 2) * object.dimen[1];
             printf("The volume is %.4lf\n", object.volume);
            break;
    }

    numColor[object.color]++;
    rawColor[object.color] -= object.volume;
    numShapes[object.shape]++;
        return object;
}

and implementing them here:

const char nameShapes[SC_COUNT][10] = {"Cube", "Cubiod", "Sphere", "Cylinder", "Cone"};
const char colorNames[CC_COUNT][10] = {"Red", "Green", "Blue", "Black"};
const char objsize[4][10] = {"Small", "Medium", "Large", "Giant"};

void DisplayStatistics()
{
    ObjectData output;
    output.index = g_objectCount;
    output.valid = true;
    output.printed = true;
    double total;
    int userInput;
    double small = 0.0, medium = 0.0;
    double large = 0.0, huge = 0.0;

    int maxCount = 0;
    int maxShape = -1;

    printf("Which would you like to see\n");
    printf(" 1 - Percentage of colors printed\n");
    printf(" 2 - Popular 3D shape printed\n");
    printf(" 3 - Most common object size by volume\n");
    printf("Enter your choice: ");
    scanf("%d\n", &userInput);

    switch (userInput) {
        case 1:
            for(int i= 0; i < CC_COUNT; i++) {
                total= (numColor[i] / (double) output.index) * 100;
                printf("Color percentage for %s: %.2f%%\n",colorNames[i],total);

            }
            break;
        case 2:
            for(int shape = 0; shape < SC_COUNT; shape++){
                if(maxCount < numShapes[shape]){
                    maxCount = numShapes[shape];
                    maxShape = shape;
                }
            }
            printf("The most popular shape is %s\n", nameShapes[maxShape]);
            break;
        case 3:
            if(output.volume > 0 && output.volume <= 1.0){
                small++;
            }
            if(output.volume > 1.0 && output.volume <= 10.0){
                medium++;
            }
            if(output.volume > 10.0 && output.volume <= 100.0){
                large++;
            }
            if(output.volume > 100.0){
                huge++;
            }

            small = (small / output.index) * 100;
            medium = (medium / output.index) * 100;
            large = (large / output.index) * 100;
            huge = (huge / output.index) * 100;

            printf("Small %.2f% % \n", small);
            printf("Medium %.2f% % \n", medium);
            printf("Large %.2f% % \n", large);
            printf("Huge %.2f% % \n", huge);
            break;
        default:
    }
}

I need to compare the volume's and display the most common size and i was told to take a similar approach as I did in the first two but Im confused on how. im trying to display it in case 3 btw